1. Field of the Invention
The present invention relates to air filter units which are stationary in use, and which include a rotatable mounting to permit the filter cartridge to be rotated under centrifugal force for cleaning without removal.
2. Prior Art
My U.S. Pat. No. 3,998,656 teaches the importance of cleaning cylindrical air filters, and in particular cleaning pleated type paper cartridges and other hollow cylindrical filters by centrifugal force combined with a forced reverse airflow. The device shown therein requires the removal of the air filter cartridge from the filter housing on the vehicle or internal combustion engine with which it is used.
Other devices in the prior art include centrifugal filters which are rotated for filtering action, usually comprising a perforated rotatable drum in a housing to provide air filtering action from the centrifugal force on the rotating unit. This type of filter is not adapted for static operation, and generally does not have as efficient operation as a stationary paper type pleated filter. The centrifugal cleaning action also tends to reduce airflow through the element. Such a device is shown in U.S. Pat. No. 3,857,687 and also in U.S. Pat. No. 3,907,529 for typical showing.
Other air cleaner devices are used which utilize baffles to cause a circumferential flow of air. Patents which illustrate this principle include U.S. Pat. Nos. 3,672,130; 3,740,932; 3,616,618; 3,670,480; and 3,078,650. These devices primarily rely upon the principle of having the air itself rotating or moving annularly so that the entrained particles will be thrown outwardly from the air, while the filter element remains stationary.
U.S. Pat. No. 3,898,066 shows a rotating filter element within a housing that is operated by turbine blades to rotate the filter housing during use from the air that passes through the filter.
An early type air cleaner is shown in U.S. Pat. No. 1,340,058 wherein a plurality of blades rotate during use to attempt to utilize centrifugal force to separate dust from the incoming air in an internal combustion engine.